Refining of mineral oils



March e, 1945. J, STA@ ET AL 2,370,819

REFINING OF MINERAL OILS Filed Dec. 17, 1940 .SM/EETENEP @IL OUTLET EMULSlQ/V THAI/4 MIX/IVG CHA MER SUL F072 GIL SEPARRTRJD 011- 7o .s-rovlzA GE PGENEZAT/NC au. 'FREE .SUL'PHIDE SPENTOQ T972 LINE AIR MAE? REGENERATED .DocvfOP To MIX/Nc CHAMBER Patented Mar. 6, 1945 UNITED STATES PATEN T OFFICE REFINING OF MINERALOILS .Irxzingl:Staid,1Medford, and Joseph E. Murphy,

-EverettMa'ss., assgnors to :Standard lGil Development Company, a corporation of v Delaware -Applicaton'becember 17, 1940, "Serial No. 370,'46'0 (Cl. 19d-33) -:4 Claims.

This .invention is Acomserneol -with the refining oi mineral oils. The'invention "ls Amore vparticu-- 'larly 'concerned `with thereflriing jof 'petroleum oils as, for example, motorffuels and similar-produc'ts and especially relates "to 'a process and Aapparatus for treating sulfur-containing oils with sodium 'plumbite or analogous lead compounds vfor 'therpurpose lo'f removing lobjactionable 'sulfur rcompounds therefrom. The invention is ymore lparticularly :directed `to Aan improvement in the 'so-'called doctor sweetening operation by which high quality petroleum products are secured and 'in which material economiesin 'the processare effected. In 'accordance with the 'present process, the lead mercaptides -are converted to disul- -des and lead oxides by utilizing ya novel procedure which Vmaterially vimproves the operation and eliminates inherent Jdisadvantages heretotore secured due to *the emulsions'which bform.

Mineral oil distillates, as for example, petroleum oil distillates Iboilinfgin the kerosene rand motor 'fuel 'boiling range vcontain certain sulfur "compounds which "impart disagreeable odors to the oils. "Various methods have been jemployed for the removal of these 4compounclsor 'for `the 'conversion of these :disagreeable sulfur com- 'pounds to innocuous materials. However, these.

.compounds 'are usually removed'by agitating the oils with ,an 'alkalirnetal'plumbite solution such as .a sodium 4plumbite solution .which vis prepared b y dissolving lead oxide in 'an excess of sodium "hydroxide, The'petrdleum oil and plumbite solution are mixed and .a chemical reaction occurs, resultinglin'the conversion -of mercaptans'to corresponding lead meroaptides. 'These 'mercapg tides are lthen decomposed 'usually'by the addif tion. of freesulfur resulting lin lthelead ,being precipitate'd las .an :insoluble leadisulde .and .in the formation .of sodorless .'disuliide compounds, [This ,operation 'known Aas sweetening may be'..sum marized by the ,following reactions.:

rr) Pisoqgzuaorrauaesosvfmo 12) fzasuJsuaseeozeebrasngtzuaou rcs) rscnsiatserfbsufussa generation. Various suggestions have been made 'f or overcoming these Iinherent difficulties 'result-l ing rvfronrthe '.ia'ct that undesirable Aemulsions `form; The proposed methods are more .or'lless cumbersome and are 'not ventirely*satisfactory from a vcommercial ,standpoint 'For example, various eleotrolytic .precipitation methods `have been suggested which materially 'increase fthe overall costs oith'e operations.

We'have nowdiscovered aprocess'by which oils may be treated inthe usual manner withan-.a'lkali metal plumbite solution .and 'the treated products readily separated rom'thespen't'solution in a continuous and efficient operation. Our 'inven-` tion comprises passing 'the oil solutionl and 'the added doctorslution, as well .as A.the added sulfur into a settling zone, 'from 'the top of which .treated oil `free 'from undesirable sulfur constituents 'is withdrawn. In accordance with ourgprocess .there is .withdrawn from an 'intermediate `point in the settling zone, .a vstream .compr'ising 'the emulsion. 'I-his stream is ,passed through an Aemulsionbreaking .zone .and handled inia .manner .to nompletely .separate .the V,spent .doctor from .the separated .o'l. .The spent doctor Asolution removed from Athis stream .is .combined `.with the total vvol-- ume of spent doctor solution whichis `withdrawn from the bottom of the separation zone while the oil is combined with the -oil removed overhead tromfthe -separation-.zone.

The process -of four rinven'tion may be 'readily understood -lby reference tothe attached fdraw ing .illustrating onel `rnodiiication :of :the same. For 1purposes :of description; ithe )feed :oil is taken to -be a .mercaptan containing petroleum cracked naphtha boiling in the motor fuel boilingmange. The sour feed .oil .containing the -mercaptans is introduced into .the system by means of feed line l. alkalifmetalfplumbite solution, Which for the ,purposes o'f description is assumed to be a sodium -plumbite solution, -i-s --combined with the untreated oil fbys-means of line .2 .and the mixture passed -into mixing vcharrlber f3. An -oil lsolution of sulfur vis introduced .into vmixing fclfiancrbei' 3 by .means ,of .line 4. This .mixture .is withdrawn from mixing :chamber 13 by unean's -.of line 5 fand ipassed `into .settling zone 6 :in 'which an oil phase vforms which rises to the top :of lsettling zone @6. A spent doctor 'phase -forms in the bottom of settling zone 6 -while'fthe .emulsion layer .-forms :at :the interface between the -oil and the Yspent .doctor. ,In 5accordance with four operation, `the treated oil is fwithdrawn from.settling zonet by means of line 1 l:and the spent-doctor solution phase 'withdrawn by :means of line lil. The vemulsion `phase :is -wthdrawn1from settling zone 6 by means of .line r9 aand passed -into emulsion storage -tank Ml :fromfwhich it is withdrawn by'rneans :of .pump v=l 5 :and Vpassed .into ldemulsilication zone I5 which comprises any suitable dezone may comprise a single unit 2| or any other number and arrangement of units. For the purpose of description, it is assumed that the. regeneration zone comprises units 2i and 22 which may be operated in series or parallel. The re generated doctor solution is preferably recycled to the treating zone by means of lines 23 and' 24.

The process of the present invention may be widely varied. Although elevated temperatures and pressures may be employed, it is preferred to contact the motor fuel and the doctor'solution at ordinary temperatures and pressures. In accordance with a preferred modication of the invention, an automatic liquid level controller is maintained on the settling tower which controls the withdrawal rate of the spent doctor solution. The emulsion which forms at the interface of the oil and spent doctor solution is withdrawn continuously and passed either directly or by way of an intermediate storage tank Vto demulsifying zone wherein the oil and spent doctor solution are separated. The oil free of objectionable sulfur compounds and spent doctor solution is removed continuously and the separated doctor solution is removed continuously and the separatedl doctor solution regenerated.

In order to illustrate the invention further, the following example is given which should not be construed as limiting the same in any manner whatsoever.

Example Continuous Conventional withdrawal withdrawal and separa and separation tion olor Light yellow.. Deep red` um-'cu. dish with no inliib 26 316. ulfur l5 5. Octane No is. 61. 0 57.0.

From the above it is apparent that the quality of the feed oil is greatly improved over that secured when using a conventiona1 method with hazard present when blowing the spent doctor with air for the regeneration of the same. An improved sweetening operation is obtained since the spent doctor solution and the sulde are withdrawn continuously to the regeneration system. This results in a constant quality regenerated doctor solution which permits a better controlled sweetening operation.

What we claim as new and wish to cover by Letters Patent is as follows:

1. Continuous process of refining petroleum oils containing mercaptans by doctor treating, which comprises continuously mixing a feed petroleum oil containing mercaptans with an alkali metal plumbite solution under conditions to ccn- .vert said mercaptans into lead mercaptides, and

with a sufficient amount of sulfur to convert said lead mercaptides to lead sulde and alkyl disul dawhereby an emulsion forms during said mixing, continuously passing the resulting mixture into a settling zone where said mixture separates continuously into three layers, an upper oil layer, a middle emulsion layer and a lower spent plum- 4 bite layer, and continuously removing each of'said fil) respect to color, gum, stability, sulfur content and octane number.

Furthermore, when employing the present process, the capacity of the doctor settler of the continuous sweetening system is increased since the emulsion is noi', allowed to build up in the tower. This results in less sulde carry-over from the settler. Furthermore, no oilreaches the doctor regeneration tanks since the spent doctor is free of oil and the oil in the emulsion is thoroughly separated. This eliminates the ire f three layers separately directly from said settling zone.

2. Process according to claim 1 in which the removed spent plumbite solution is regenerated and recycled for further doctor treating.

3. Process according to claim 1 in which the removed emulsion layer is broken into an oil phase and a spent plumbite phase and then later is regenerated and recycled for further doctor treating.

4. Continuous process for doctor sweetening of a cracked petroleum oil of the motor fuel boiling' range, which comprises continuously mixing said petroleum oil with a sodium plumbite solution under conditions to convert mercaptans to corresponding lead mercaptides, and withV an amount of sulfur suiiicient to convert the resulty ing lead mercaptide to lead sulde and alkyl disulde, whereupon an emulsion forms during said mixing, continuously passing the resulting mixture into a vertical tower settling zone where said mixture separates continuously into three layers, an upper cracked petroleum layer, substantially completely free of mercaptans, a middle emulsion layer containing a relatively small proportion of the original feed oil, some of the spent plumbite solution and some finely divided precipitated lead sulde, and a lower spent sodium plumbite solution layer substantially completely free of oil constituents, continuously removing each of said three materials separately directly from said settling zone, said upper sweetened oil layer being removed overhead, said middle emulsion layer being removed from a point in the tower intermediate between the upper oil layer and the lower spent plumbite layer, said emulsion layer being de-emulsied into an oil phase and into a spent plumbite phase containing oilfree lead sulfide, and passing said deemulsifled spent plumbite phase to a plumbite regeneration zone, also removing from the bottom of the tower settling zone the lower layer consisting of spent plumbite Solution, passing it also to the plumbite regeneration zone, regenerating the spent plumbite solution in said regeneration zone by airblowing and recycling the resultant regenerated sodium plumbite solution for further doctor sweetenins of feed oil.

IRVING J.- STAID. JOSEPH E. MURPHY. 

